VATICAN CITY — Pope Francis has urged leaders of the Group of 20 to abandon the “futile pursuit” of a military solution in Syria and work instead for dialogue and negotiation to end the conflict.

In a letter Thursday to the G-20 host, Russian President Vladimir Putin, Francis lamented that “one-sided interests” had prevailed in Syria, preventing a peaceful solution and allowing the continued “senseless massacre” of innocents.

Francis has ratcheted up his call for peace in Syria amid threatened U.S.-led military strikes following a chemical weapons attack.

He will host a peace vigil in St. Peter’s Square on Saturday. On Thursday, the Vatican summoned ambassadors accredited to the Holy See to outline its position, calling for the respect for all minorities including Christians and that Syria’s opposition forces distance themselves from extremists.